It may be a bit of a surprise that this is not an Arduino compatible board. [Ray] tried a few projects with PIC microcontrollers and ended up really liking them. He chose to go with the PIC 18F14K50 for this project. The chip has USB functionality and is running a bootloader. He thinks this makes it easier to work with over a wide range of computers than the Lilypad (a sewable Arduino compatible board which sometimes runs into FTDI driver issues the first time you try to program it).

We like the fact that it is open source. As we mentioned earlier, it comes in a few different flavors. There is a red or white version that uses a LiPo battery, and one that is driven from a CR2032 coin cell. If you’re working on a small project to which you would like to add a rechargeable battery this will serve as a cheap and easy reference design.